Laminated article and process of making same



PM Feb. 7, 19.39

PATENT OFFICE 7 2,140,034 LAMINATED narrow AND access or 1 minno- SAME John P. Sermattei, it We, N. 1., assignor to E. I. du Pont de Nemonrs & Company, Wilmine-ton, DcL, a corporation of Delaware No Drawing. Application February 5, 1935, Serial No. 5,069

Claims.

This invention relates to. adhesive compositions and more particularly to thermoplastic compositions comprising cellulose nitrate and a solventplasticizer.

5. .Heretofore thermoplastic cements have been dependent for their thermoplastic and adhesive properties on the presence in the composition of resins which soften and become sticky and adhesive on being heated and later regain their hardness when allowed to cool, thus forming the bond between the materials being; joined. In these thermoplastic adhesive compositions there is a tendency for the development of brittleness when subjected to reduced temperatures due to the large resin content of the adhesive, thereby weakening the bond. .Softeners are sometimes used in these compositions but the high resin content still has a tendency to make them brittle at reduced temperatures.

An object of the present invention is to provide a thermoplastic adhesive composition which is not'dependent for its thermoplastic and adhesive properties on the presence in the composition of either natural or synthetic resins. A further object is to provide a thermoplastic adhesive composition which does not require a high temperature to soften it and which does not change its composition during the heat treatment, thus eliminating the so-called curing of the ad- 30 hesive. 4

In order to illustrate the invention the following examples of compositions are given:

o5 Toluene Example '4 Percent I by weight Cellulose nitrate 10.0 Triphenyl phosphate 8.0 8 Ethyl acetate- 24.6 Denatured alcohol 24.6 Toluene 32.8

Theyiscosities given throughout this speciflca- 10 tion are measured in accordance with the method outlined in the A. S; T. M. Tentative Specifications and Tests for Soluble Nitrocellulose, Designation D-301-30T.

. The viscosity of the cellulose nitrate in the 16 examples given above may vary from 2 sec. up

to 80 sec. However, for special purposes, I may use cellulose nitrate having a viscosity of A see. or, on the other hand, I may use cellulose nitrate having a viscosity of 100 sec. or even higher. 20 This is a matter which will be apparent to those skilled in the art.

The preparation of the adhesive compositions in the examples above is carried out substantially in the following manner:

The so-called nonsolvents or diluents, as toluene and denatured alcohol, are first added to the cellulose nitrate in order to wet it, then the active cellulose nitrate solvents are added and then the solvent softener. The mass is thoroughly agitated and when complete dispersion is obtained, it is ready for use. The compositions described in the above examples are substantially transparent and nearly water white.

These adhesives can be applied in the usual manner either by brush, dipping, spraying, or by roller coating procedures. After the adhesive is applied to the articles which are to be adhered, the volatile solvents and diluents are allowed to evaporate until the film is dry. .Materials thus treated are then brought into contact with each other and subjected to pressure at an elevated temperature either in a press, between rolls, or by means of a hot iron. Only a slight pressure is necessary, 2 to 15 lbs. per' square inch being sufllcient, although greater pressure can be used if desired. A satisfactory working temperature range is between 130 and 200 C. Further details with regard to adhering the surface will be readily evident to those versed in the art of combining materials.

In cementing two objects together it is not necessary to apply the adhesive and then stick the two objects together at 'once. The adhesive may be applied and then allowed to dry in which 5 above. The films of adhesive when warmed begin to soften and when broughtin contact with each other become one, and. then on cooling again; thefllm returns to its tenacious, flexible and nontackycondition-j The preferred compositions in the to 8-30 parts of solvent-plasticizer, however a greater or lesser amount of solvent-plasticizer may be used with the cellulose nitrate, although it has'been found that the range mentioned gives the most satisfactory results.'

The active solvents and the diluents for the cellulose nitrate play no part in the final use of the adhesive but merely act as a means for suitably dispersing the cellulose nitrate so'that it can form a mixture with the solvent-plasticizer. The amount of active solvent and the diluent can be varied according to the viscosity or fluidity desired in the finished material.

The type of plasticizer used in the preferred form of this invention is the socalled solventplasticizer". Materials which have been found useful in this invention other than those mentioned in the above examplesare dibutyl .tartrate,

triacetin, tributyl phosphate, cyclohexyl adipate, phthalic acid esters of methyl, ethyl, butyl, amyl alcohols and of the higher aliphatic alcohols, aliphatic ethers, and phthalic acid esters of cyclohexanol, and paratoluene'sulfonamide and its derivatives. These can be used either singly or in combination. The active solvents and diluents employed are those generally used for preparing cellulose nitrate dispersions and may be varied over wide limits, such limits and choice ofma- Jterialsbeingknowntothoseskilledinthe art.

The viscomty characteristic of the cellulose nitrate is not critical, the choice depending largely on the viscosity desired for the finished adhesive,

however, the nitrogen content of the cellulose nitr'ate is important, and best results are obtained when this value isbetween 9.5% and'11.5%. v

Good results are also obtained where the nitro-' gen content lies between 11.5% and 12% and acceptable compositions may be prepared with nitroceliulose of nitrogen content up; to 12.5%. However, nitrocelluloses of nitrogen content below 12% are definitely preferred.

It is of advantage to use nitrocelluloses in the lower nitrogen range for two reasons: first, be-

'cause at a given plasticizer-nitrocellulose ratio, a

with them without producing a sticky or tacky film. This is of considerable importance where brief or extended storageof the coated surfaces is necessary before they are laminated.

The compositions may be modified by the addition of substances which are inert so far asthermoplastic properties are'concerned, forexample refined de-waxed shellac may be used.'or other materials, for example certain natural resins such g ester s m. menu.

examples I given'cover a range of parts of cellulose nitrate The natural resin which may be added plays no substantial part in providing heat energizability, its only function being to, promote adhesion when the adhesives are used in connection-with metal surfaces.- While dammar and ester gums are thermoplastic toa certain extent. in themselves, it has. been found that their action in these compositions which contain the solvent-plasticizers, is to dilute the solvent plasticizer and thus somewhat lower its thermoplastic action.

The uses of this invention are readily apparent and particularly useful in cementing regenerated cellulose sheeting together or in forming moisture proof containers therefrom. It is equally satis- L factory in joining paper, cardboard, metal foils, wood, leather, fabrics, all kinds of cloth, glassine, or any combination of suchmaterials.

This invention presents as an advantage over be coated and stored until such time-as it is desired. to carry out the combining operation. This is a decided advantage .over the use'of regular adhesives which require immediate adhesion to .another surface after being applied to a surface which will form part of the finished combined It is apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof and, therefore, it is not intended to be limited except as indicated by the appended claims.

I claim: I J

1. The process of ted materials which comprises coating at least one surface of the, materials to be joined with a thermoplastic adhesive which when free of volatile solvents is soft and sticky above about 130 C., said adhesive aside from volatile solvents consisting of nitrocellulose having aviscosity characteristic less than 80 seconds and a" nitrogen content between 9.5% and 11.5% and a solvent plasticizer, present in amount of about twice that of the nitrocellulose, allowing the adhesive to dryand subsequently Joining the parts by means of heat and pressure.

i 2. A laminated article comprising at least two non-thermoplastic components joined by means of a thermoplastic adhesive which is soft and sticky above about 130 C. and which consists essentially of nitrocellulose having a viscosity characteristic below 80 seconds and a nitrogen content between 9.5% and 11.5% and a solvent plasticizer for the nitrocellulose, said plasticizer being present in amount of about twice the amount of nitrocellulose.

s. The article of claim 2 m which at least one ofthecomponentsiscloth. I

4. The article of claim 2 in which at least one of the components is regenerated cellulose.

5. The article of claim 2- in which at least one of the components is paper. I

mm; P. manner. 

